Electromagnetic impedance spectroscopy apparatus and related planar sensor system

Abstract

According to various implementations, an apparatus for electromagnetic impedance spectra graphic characterization of a material under test (MUT) includes: a planar array of at least two electrodes configured to be placed in electromagnetic communication with the MUT, wherein during operation of the planar array, at least one of the electrodes comprises a transmitting electrode for transmitting an electromagnetic signal over a range of frequencies through the MUT to at least one receiving electrode in the planar array; and a backer ground plate at least partially surrounding the at least two electrodes, the backer ground plate being electrically grounded and insulated from the at least two electrodes, wherein the backer ground plate extends from a plane formed by the at least two electrodes and separates the at least two electrodes to create an electrically isolated volume proximate to the at least two electrodes.

What is claimed is: 
     
       1. An apparatus comprising:
 a planar sensor array of at least two electrodes configured to be placed in electromagnetic communication with a material under test (MUT), wherein during operation of the apparatus, at least one of the electrodes comprises a transmitting electrode for transmitting an electromagnetic signal over a range of frequencies through the MUT to at least one receiving electrode in the planar sensor array; and 
 a conductive backer ground plate at least partially surrounding the at least two electrodes, the conductive backer ground plate being electrically grounded and insulated from the at least two electrodes, wherein the conductive backer ground plate extends from a plane formed by the at least two electrodes and separates the at least two electrodes to create an electrically isolated volume proximate to each of the at least two electrodes, 
 wherein the conductive backer ground plate extends between neighboring electrodes in the sensor array and defines a set of separate volumes corresponding with each of the at least two electrodes, wherein the electrically isolated volume proximate each of the at least two electrodes is configured to mitigate parasitic impedance impacts from the electromagnetic signal received at a neighboring one of the at least two electrodes. 
 
     
     
       2. The apparatus of  claim 1 , wherein the plane formed by the at least two electrodes and the conductive backer ground plate is substantially parallel with a surface of the MUT. 
     
     
       3. The apparatus of  claim 2 , wherein the array of at least two electrodes comprises axisymmetric circular electrodes, wherein a first one of the at least two electrodes comprises a central electrode and a second one of the at least two electrodes comprises an outer electrode. 
     
     
       4. The apparatus of  claim 3 , wherein the central electrode comprises the transmitting electrode and wherein the outer electrode comprises the receiving electrode. 
     
     
       5. The apparatus of  claim 3 , wherein the central electrode comprises the receiving electrode and wherein the outer electrode comprises the transmitting electrode. 
     
     
       6. The apparatus of  claim 1 , wherein the planar sensor array is arranged in a linear rectangular configuration, wherein a first one of the at least two electrodes is a transmitting electrode and a second one of the at least two electrodes is a receiving electrode. 
     
     
       7. The apparatus of  claim 1 , wherein a spacing of the conductive backer ground plate between the transmitting electrode and receiving electrode is sized to adjust for a depth of penetration and measurement into the MUT. 
     
     
       8. The apparatus of  claim 1 , wherein each of the at least two electrodes has a rectangular shape with rounded corners. 
     
     
       9. The apparatus of  claim 1 , wherein the array of at least two electrodes comprises at least three electrodes arranged in a linear rectangular configuration. 
     
     
       10. The apparatus of  claim 1 , wherein a single electrode in the planar sensor array comprises the transmitting electrode and the remaining electrodes in the planar sensor array comprise the at least one receiving electrode. 
     
     
       11. The apparatus of  claim 5 , wherein the planar sensor array comprises a plurality of transmitting electrodes and a plurality of receiving electrodes. 
     
     
       12. The apparatus of  claim 11 , wherein the transmitting electrode is selectable among the electrodes of the planar sensor array, and is configured to change between the electrodes of the planar sensor array. 
     
     
       13. The apparatus of  claim 1 , wherein during operation of the apparatus, the planar sensor array is in direct physical contact with the MUT and is either electrically non-conductive with the MUT or electrically conductive with the MUT. 
     
     
       14. A system comprising:
 an apparatus for communicating with a material under test (MUT), the apparatus comprising:
 a planar sensor array of at least two electrodes configured to be placed in electromagnetic communication with the MUT, wherein during operation of the apparatus at least one of the electrodes comprises a transmitting electrode for transmitting an electromagnetic signal over a range of frequencies through the MUT to at least one receiving electrode in the planar sensor array; and 
 a conductive backer ground plate at least partially surrounding the at least two electrodes, the conductive backer ground plate being electrically grounded and insulated from the at least two electrodes, wherein the conductive backer ground plate extends from a plane formed by the at least two electrodes and separates the at least two electrodes to create an electrically isolated volume proximate to the at least two electrodes, 
 wherein the conductive backer ground plate extends between neighboring electrodes in the sensor array and defines a set of separate volumes corresponding with each of the at least two electrodes, wherein the electrically isolated volume proximate each of the at least two electrodes is configured to mitigate parasitic impedance impacts from the electromagnetic signal received at a neighboring one of the at least two electrodes; and 
 
 a circuit coupled with the apparatus, the circuit configured to transmit a set of electromagnetic signals through the planar sensor array through the MUT, and receive at least one return signal from the planar sensor array. 
 
     
     
       15. The system of  claim 14 , wherein the circuit includes a signal generator operating over a range of frequencies for transmitting the electromagnetic signal from the transmitting electrode of the planar sensor array through the MUT and a signal analyzer configured to analyze the at least one return signal,
 wherein the circuit further includes a computing device coupled with the signal analyzer, wherein the computing device is configured to determine a physical property of the MUT based upon the transmitted electromagnetic signal and the at least one return signal, 
 wherein determining the physical property of the MUT comprises:
 transmitting the electromagnetic signal over a range of frequencies from the transmitting electrode through the MUT to the receiving electrode; 
 comparing the transmitted electromagnetic signal to the received signal to compute an electromagnetic property of the MUT; and 
 correlating the computed electromagnetic property of the MUT with a physical property of the MUT to determine the physical property of the MUT. 
 
 
     
     
       16. The system of  claim 14 , wherein during operation of the system, the planar sensor array is in direct physical contact with the MUT and is either electrically non-conductive with the MUT or electrically conductive with the MUT. 
     
     
       17. The apparatus of  claim 7 , wherein the transmitting electrode has a first length (L 1 ), a separation between the transmitting electrode and the receiving electrode has a second length (L 2 ), and the receiving electrode has a third length (L 3 ), wherein the second length (L 2 ) causes a portion of electromagnetic field lines from the electromagnetic signal to be intercepted by the conductive backer ground plate to mitigate the parasitic impedance. 
     
     
       18. The apparatus of  claim 17 , wherein L 2  is greater than L 3 . 
     
     
       19. The apparatus of  claim 18 , wherein L 1  is greater than L 3 . 
     
     
       20. The system of  claim 14 , wherein the transmitting electrode has a first length (L 1 ), a separation between the transmitting electrode and the receiving electrode has a second length (L 2 ), and the receiving electrode has a third length (L 3 ), wherein the second length (L 2 ) causes a portion of electromagnetic field lines from the electromagnetic signal to be intercepted by the conductive backer ground plate to mitigate the parasitic impedance, wherein at least one of the following dimensional relationships exists:
 a) L 2  is greater than L 3 , or 
 b) L 1  is greater than L 3 .